Water-soluble AZO compound or salt thereof, ink composition, and colored article

ABSTRACT

Disclosed are: a yellow dye which has a color phase having a high contrast ratio suitable for inkjet recording, can produce recorded materials having high durability, and can be used for the preparation of an ink composition to provide an ink composition having excellent storage stability; and an ink composition containing the yellow dye. Specifically disclosed are: a water-soluble azo compound represented by formula (1) or a salt thereof; and an ink composition containing the compound or the salt thereof. The ink composition has a color phase and a color saturation suitable for inkjet recording, can produce recorded materials having high durability, particularly high light resistance and ozone gas resistance, and can also produce printed images having excellent storage stability or the like. In the formula, Q represents a halogen atom; R represents a C1-C11 alkylene group; p represents an integer of 2 to 4; and n represents 1 or 2.

This application is the U.S. National Phase under 35 U.S.C. §371 ofInternational Application PCT/JP2010/056516, filed Apr. 12, 2010,designating the U.S., and published in Japanese as WO 2010/125903 onNov. 4, 2010, which claims priority to Japanese Patent Application No.2009-109545, filed Apr. 28, 2009, and Japanese Patent Application No.2009-203199, filed Sep. 3, 2009, the entire contents of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a water-soluble disazo compound or asalt thereof, an ink composition containing the same, and a coloredarticle which was colored therewith.

BACKGROUND ART

For a recording method by an ink jet printer, which is one typicalmethod among a variety of color recording methods, a variety of inkdischarge systems have been developed. These systems execute recordingby generating ink droplets, which are adhered onto any of a variety ofrecord-receiving materials (e.g., paper, film, and fabric, etc.).According to this method, a recording head is not brought into directcontact with the record-receiving material; therefore, generation ofnoise can be avoided thus achieving silent recording. In addition, dueto having the feature of reduced size, increased speed and coloringbeing readily achievable, prevalence in recent years has been in rapidprogress, and thus great advancement hereafter is expected.

Inks containing a water-soluble coloring matter (dye) dissolved in anaqueous medium have been used as conventional inks for fountain pens,felt pens etc., and inks for ink jet recording. To these inks isgenerally added a water-soluble organic solvent in order to prevent pentips or ink discharge nozzles from clogging with the ink. For theseinks, demanded are performances such as ability to generate a recordedimage with satisfactory density, probability of avoiding occurrence ofclogging at the pen tips and nozzles, favorable drying characteristicson the record-receiving materials, suppression of bleeding, superiorstorage stability, and the like.

Clogging of nozzles of ink jet systems often results from hardening anddeposition of a coloring matter when the moisture of the ink evaporatesfaster than other solvent and additives in the vicinity of the nozzle tocause a state of the composition including less moisture and asubstantive amount of the solvent and additives. Therefore, oneextremely important expected performance is that solids are less likelyto be deposited even in the state in which the ink contains a low amountof moisture. On this ground, high solubility in the solvent andadditives is also a property required for coloring matters. Also, in aknown procedure for resolving a problem of clogging of nozzles, acoloring matter capable of providing a high print density is used. Byusing a coloring matter having a high print density, the content of thecoloring matter in an ink can be reduced while maintaining a printdensity according to conventional procedures. This not only results inreduction of probability of deposition of the coloring matter, but alsois advantageous in terms of costs, and thus development of a coloringmatter having higher print density has been desired.

In the meantime, for recording image or character information on a colordisplay of computers in full color by an ink jet printer, subtractivecolor mixing with four inks having different colors of, generally yellow(Y), magenta (M), cyan (C), and black (K) has been employed, whereby therecorded image is presented in full color. In order to reproduce anadditive color mixing image formed with red (R), green (G), blue (B) ona CRT (cathode ray tube) display and the like as strictly as possibleusing subtractive color mixing, it is desired that Y, M and C, among thecoloring matters used in inks, have a hue approximate to the standardcolor, and are brilliant, respectively. The term brilliance as hereinreferred to means, in general, to have a high chroma saturation. Whenthree primary colors of Y, M and C having a low chroma saturation areused, narrowing occurs of the color region that can be expressed by asimple color or a mixed color, whereby the range of the color region tobe expressed may be insufficient. Therefore, development of a coloringmatter having a high chroma saturation, and an ink containing the samehave been desired.

In addition, long term storage stability, as well as high density of therecorded image, and superior fastness such as water resistance, moistureresistance, light resistance and gas resistance of the image are alsorequired properties for the inks. Herein, gas resistance meansresistance to a phenomenon of causing discoloration and fading of arecorded image via a reaction of a gas present in the air and having anoxidizing action, with a coloring matter (dye) of the recorded image onor in the record-receiving material. Particularly, ozone gas amongoxidizing gasses is considered as a main causative substance thatpromotes the discoloration and fading phenomenon of ink jet recordedimage. Since this discoloration and fading phenomenon is characteristicin ink jet recorded images, improvement of the ozone gas resistance is asignificant technical problem in the art.

Advancement of ink jet techniques in recent years has lead to aconsiderable increase in the speed of ink jet recording (printing).Thus, similarly to laser printers using an electronic toner, use of inkjet printers has started for printing of documents on plain paper whichhas a main application in office environments. Prevalence of the ink jetprinters has been in progress particularly in small to medium scaleoffice environments such as SOHO in particular, due to advantages suchas no limitation of usable recording paper, and low cost of the printeritself. When an ink jet printer is thus used for applications inprinting on plain paper, hue, color formation (printing) density andwater resistance tend to be regarded more importantly among qualitiesrequired for printed matter.

For the purpose of achieving these performances, a method in which apigment ink is used was proposed. However, pigment inks do not have astate of solution as the coloring matter is not dissolved in an aqueousink, but have a state of dispersion. Therefore, use of a pigment ink inink jet recording may involve problems of stability of the ink per se,problems of clogging of nozzles of recording heads, and the like. Inaddition, when a pigment ink is used, a problem in connection withabrasion resistance often occurs. In the case of the dye inks, theaforementioned problems are reported to be comparatively less likely tooccur; however, dye inks are significantly inferior particularly inwater resistance as compared with pigment inks, and improvement of thisdisadvantage has been strongly desired. In addition, unlike pigmentinks, dye inks are likely to involve problems of lowered coloringdensity as a result of faster permeation of the coloring matter adheredonto the surface of a plain paper by ink jet recording toward the backface direction of the paper.

In one method for attaining ink jet recorded images of photo imagequalities, an ink receiving layer may be provided on the surface of arecord-receiving material. In an ink receiving layer which is providedfor such a purpose, a porous white inorganic substance is often includedfor facilitating drying of the ink and for minimizing bleeding of thecoloring matter to provide high quality images. However, discolorationand fading due to ozone gas is markedly observed particularly on such arecord-receiving material. Along with recent prevalence of digitalcameras and color printers, the opportunity for printing images withphoto image quality obtained by a digital camera or the like haveincreased also at home. Thus, discoloration and fading of the recordedimage due to the oxidizing gas as described above has been a concern.With regard to yellow coloring matters, those having favorableresistance against oxidizing gas as well as light resistance have beenproposed, as compared with others among three primary colors, i.e.,magenta and cyan. However, yellow coloring matters for ink jet recordingand yellow inks having high brilliance required for market, and alsohaving various types of fastness properties that are sufficientlysatisfactory have not yet been obtained.

As a well-known yellow coloring matter for ink jet that is superior inwater solubility and brilliance, C. I. (Color Index) Direct Yellow 132is exemplified. Furthermore, a plurality of azo yellow coloring mattershaving superior fastness properties have been proposed on the basis ofdevelopment of yellow coloring matters for ink jet recording in recentyears.

-   Patent Document 1 discloses an anionic azo yellow compound having    light resistant and water resistant fastness.-   Patent Document 2 discloses a water-soluble yellow azo compound    having high solubility in water, moisture resistance, ozone gas    resistance, and light resistance.-   Patent Document 1: Japanese Unexamined Patent Application,    Publication No. H4-233975-   Patent Document 2: Japanese Unexamined Patent Application,    Publication No. 2006-152264

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

An object of the present invention is to provide a water-soluble yellowcoloring matter (compound) having high solubility in water or awater-soluble organic solvent, having ability to provide high printdensity of an image recorded on particularly exclusive ink jet paper,and having ability to provide an image that is superior in lightresistance and ozone gas resistance. Another object of the presentinvention is to provide a yellow ink composition for various types ofrecording, particularly for ink jet recording, which contains the yellowcoloring matter.

Also, a still further object of the present invention is to provide awater-soluble yellow coloring matter (compound) having high solubilityin water, and having ability to provide the recorded image that issuperior in chroma saturation, light resistance and ozone gasresistance. Yet another object of the present invention is to provide ayellow ink composition for various types of recording, particularly forink jet recording, which contains the yellow coloring matter.

Means for Solving the Problems

In order to solve the foregoing problems, the present inventorsthoroughly investigated, and consequently found that a water-solubledisazo compound represented by a certain formula, and an ink compositioncontaining the same solve the problems described above. Thus, thepresent invention was completed.

Accordingly, a first aspect of the present invention provides awater-soluble azo compound represented by the following formula (1) or asalt thereof:

in the formula (1), Q represents a halogen atom; R represents a C1-C11alkylene group; p represents an integer of 2 to 4; and n represents 1 or2.

A second aspect of the invention provides the water-soluble azo compoundor a salt thereof according to the first aspect, in which thewater-soluble azo compound is represented by the following formula (2):

in the formula (2), q represents an integer of 1 to 11, and Q and p areas defined in the formula (1).

A third aspect of the invention provides the water-soluble azo compoundor a salt thereof according to the second aspect, in which in the aboveformula (2), p is 3, and q represents an integer of 1 to 5.

A fourth aspect of the invention provides the water-soluble azo compoundor a salt thereof according to the second aspect, in which thewater-soluble azo compound is represented by the following formula (3):

A fifth aspect of the invention provides the water-soluble azo compoundor a salt thereof according to the first aspect, in which thewater-soluble azo compound is represented by the following formula (4):

in the formula (4), r represents an integer of 1 to 4, and Q and p areas defined in the formula (1).

A sixth aspect of the invention provides the water-soluble azo compoundor a salt thereof according to the fifth aspect, in which in the aboveformula (4), Q is a chlorine atom; p is 3; and r is 1 or 2.

A seventh aspect of the invention provides the water-soluble azocompound or a salt thereof according to the fifth aspect, in which thewater-soluble azo compound is represented by the following formula (5):

An eighth aspect of the invention provides an ink composition containingthe water-soluble azo compound or a salt thereof according to any one ofthe first to seventh aspects.

A ninth aspect of the invention provides the ink composition accordingto the eighth aspect further containing a water-soluble organic solvent.

A tenth aspect of the invention provides the ink composition accordingto the eighth or ninth aspect, in which the ink composition is utilizingin ink jet recording.

An eleventh aspect of the invention provides an ink jet recording methodincluding discharging ink droplets in response to recording signalsusing the ink composition according to any one of the eighth to tenthaspects as an ink to allow the droplets to adhere onto arecord-receiving material thereby executing recording.

A twelfth aspect of the invention provides the ink jet recording methodaccording to the eleventh aspect, in which the record-receiving materialis a communication sheet.

A thirteenth aspect of the invention provides the ink jet recordingmethod according to the twelfth aspect, in which the communication sheetis a plain paper or a sheet having an ink receiving layer containing aporous white inorganic substance.

A fourteenth aspect of the invention provides a colored matter which wascolored with any one of:

(a) the water-soluble azo compound or a salt thereof according to anyone of the first to seventh aspects;

(b) an ink composition containing the water-soluble azo compound or asalt thereof according to any one of the first to seventh aspects; or

(c) an ink composition containing the water-soluble azo compound or asalt thereof according to any one of the first to seventh aspects and awater-soluble organic solvent.

A fifteenth aspect of the invention provides a colored article in whichthe coloring was carried out with the ink jet recording method accordingto the eleventh aspect.

A sixteenth aspect of the invention provides an ink jet printer equippedwith a vessel containing the ink composition according to the eighthaspect.

Effects of the Invention

The water-soluble azo compound represented by the above formula (1) or asalt thereof of the present invention is characterized by having highsolubility in water, and having favorable filterability on, for example,membrane filters, in the step of producing an ink composition of thepresent invention containing the compound or salt thereof.

Particularly, the ink composition containing the water-soluble azocompound represented by the above formula (2) or a salt thereof providesa hue of a yellow color with a high print density on an exclusive inkjet paper. Moreover, the ink composition containing this compound alsoenables photographic color images to be strictly reproduced on paper.Additionally, an ink composition containing this compound has higherprint density as compared with conventional coloring matters, and isalso superior in fastness properties such as light resistance and ozonegas resistance.

In addition, images recorded with an ink composition containing thewater-soluble azo compound represented by the above formula (4) or asalt thereof is more superior in chroma saturation, light resistance,and ozone gas resistance as compared with conventionally obtainedimages.

Accordingly, the water-soluble azo compound represented by the formula(1) or a salt thereof of the present invention, and an ink compositioncontaining the same are extremely useful for applications as varioustypes of inks for recording, particularly applications as inks for inkjet recording.

PREFERRED MODE FOR CARRYING OUT THE INVENTION

The present invention is explained in detail below.

The water-soluble azo compound represented by the above formula (1) or asalt thereof of the present invention is a water-soluble yellow coloringmatter. Unless otherwise stated in particular herein, acidic functionalgroups such as sulfo groups and carboxy groups are represented in theform of their free acids. Although the present invention involves both awater-soluble azo compound represented by the formula (1) and a salt ofthe compound as described above, description of both terms such as“compound or salt thereof”, etc., for every appearance would make thespecification complicated. Thus, in order to avoid complexity, unlessotherwise particularly stated, “(water-soluble azo) compound or a saltthereof” in the following is expediently referred to merely as“(water-soluble azo) compound” and includes the compound and salt.

The compound of the present invention is represented by the aboveformula (1).

In the formula (1), Q represents a halogen atom. Specific examples of Qinclude a fluorine atom, a chlorine atom, a bromine atom, and an iodineatom, more preferably a fluorine atom or a chlorine atom, andparticularly preferably a chlorine atom.

In the formula (1), R represents a C1-C11 alkylene group. This C1-C11alkylene group may be either straight or branched, and is morepreferably straight. The number of carbon atoms in the alkylene groupfalls within the range of more preferably C1-C5, and even morepreferably C2-C3. Specific examples include methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylece,decylene, undecylene, and the like.

In the formula (1), p represents an integer of 2 to 4, and preferably 3.

Further, n represents 1 or 2.

Among the compounds represented by the above formula (1), preferred arecompounds represented by the above formula (2) and formula (4). Also,among the compounds represented by the above formula (2) and formula(4), preferred are compounds represented by the above formula (3), andcompounds represented by the above formula (5), respectively.

In the formula (2), q represents an integer of 1 to 11, preferably aninteger of 1 to 5, and more preferably 2.

In the formula (4), r represents an integer of 1 to 4, preferably 1 or2, and more preferably 2.

Q and p used suitably in the formula (2) and formula (4) mean similarlyto the definitions in the above formula (1), including preferableoptions and the like.

With respect to Q, R, p, q, r, and n suitably used in the compoundsrepresented by the above formula (1), formula (2), and formula (4),compounds in which preferable options are combined are more preferred,and compounds in which more preferable options are combined are stillmore preferred. The same is applied to any combinations of even morepreferable options and further more preferable options, and the like.

The water-soluble azo compound of the present invention represented bythe above formula (1) can be produced, for example, as in the following.It is to be noted that Q, R, p, q, r, and n suitably used in thefollowing formula (A) to formula (H) mean similarly to the definitionsin the above formula (1), formula (2) and formula (4), respectively.

The compound represented by the following formula (A) obtained accordingto the method disclosed in Japanese Unexamined Patent Application,Publication No. 2004-75719 using 2-amino-4-halogenophenol, acommercially available product, as a basic material is converted into amethyl-ω-sulfonic acid derivative (B) using sodium bisulfite andformalin. Next, 5-aminoisophthalic acid represented by the followingformula (C) is diazotized by a routine method, and the product issubjected to a coupling reaction at a reaction temperature of 0 to 15°C. and a pH of 2 to 4 with the methyl-ω-sulfonic acid derivative of theformula (B) obtained above, and subsequently subjected to a hydrolyzingreaction at a reaction temperature of 80 to 95° C. and a pH of 10.5 to11.5 to obtain a compound represented by the following formula (D).

Subsequently, the compound (2 equivalents) of the above formula (D) iscondensed with cyanuric halide (1 equivalent), for example, cyanuricchloride (1 equivalent) at a reaction temperature of 15 to 45° C. and ata pH of 5 to 8 to obtain a compound of the following formula (E).

The compound of the present invention represented by the above formula(1) can be obtained by further substituting a chlorine atom on atriazine ring in the obtained compound represented by the above formula(E) with primary amine represented by the following formula (F) under acondition of a reaction temperature of 75 to 90° C. and a pH of 7 to 9.

In particular, the compound represented by the above formula (2) orformula (4) can be obtained by substituting a chlorine atom on atriazine ring in the compound of the above formula (E) with primaryamine represented by the following formula (G) or formula (H).

Specific examples of the compound of the above formula (G) includeglycine, β-alanine, 4-aminobutyric acid, 5-aminovaleric acid,6-aminohexanoic acid, 7-aminoheptanoic acid, 12-aminododecanoic acid,and the like.

Specific examples of the compound of the above formula (H) includeaspartic acid, glutamic acid, 2-aminoadipic acid, 2-aminopimelic acid,and the like.

Specific examples of the compound represented by the above formula (2)are presented in Table 1 below, and specific examples of the compoundrepresented by the above formula (4) are presented in Table 2 below. InTable 1 and Table 2, acidic functional groups such as carboxy group andsulfo group are represented in the form of their free acids.

TABLE 1 Com- pound Num- ber Q p q Structural formula 1 Cl 2 2

2 Cl 3 2

3 Cl 4 2

4 Cl 3 1

5 Cl 4 3

6 Cl 4 4

7 Cl 4 5

8 Cl 4 6

9 Cl 4 11 

10 Cl 3 3

11 Cl 3 4

12 Cl 3 5

13 Cl 3 6

14 Cl 3 11 

TABLE 2 Compound Number Q p r Structural formula 15 Cl 2 2

16 Cl 3 2

17 Cl 4 2

18 F 3 2

19 Br 3 2

20 I 3 2

21 Cl 3 1

22 Cl 3 3

23 Cl 3 4

The compound of the above formula (1) is present in the form of either afree acid or a salt thereof. The salt of the compound of the aboveformula (1) may be a salt with an inorganic or organic cation. Specificexamples of the inorganic cation salt include alkali metal salts, forexample, lithium salts, sodium salts, potassium salts; and ammoniumsalts. Furthermore, the organic cation may include, for example, aquaternary ammonium represented by the following formula (6), but notlimited thereto.

In the above formula (6), Z¹ to Z⁴ each independently represent ahydrogen atom, a C1-C4 alkyl group, a hydroxy(C1-C4)alkyl group, or ahydroxy(C1-C4)alkoxy(C1-C4)alkyl group, and at least one of Z¹ to Z⁴ isa group other than a hydrogen atom.

Wherein, examples of the C1-C4 alkyl group in Z¹ to Z⁴ include methyl,ethyl, and the like. Similarly, examples of the hydroxy(C1-C4)alkylgroup include hydroxymethyl, hydroxyethyl, 3-hydroxypropyl,2-hydroxypropyl, 4-hydroxybutyl, 3-hydroxybutyl, 2-hydroxybutyl, and thelike. Similarly, examples of the hydroxyl(C1-C4)alkoxy(C1-C4)alkyl groupinclude hydroxyethoxymethyl, 2-hydroxyethoxyethyl,3-(hydroxyethoxy)propyl, 3-(hydroxyethoxy)butyl, 2-(hydroxyethoxy)butyl,and the like.

Among the aforementioned salts, preferable salts include alkali metalsalts such as sodium, potassium and lithium salts; organic quaternaryammonium salts such as monoethanolamine, diethanolamine,triethanolamine, monoisopropanolamine, diisopropanolamine andtriisopropanolamine salts; ammonium salts; and the like. Of these, morepreferred are lithium salts, sodium salts, and ammonium salts.

As would be apparent to persons skilled in the art, salts or free acidsof the compound represented by the above formula (1) can be easilyobtained with the following method and the like.

A sodium salt, etc., of the compound represented by the above formula(1) can be obtained as a wet cake by isolating by filtration of a soliddeposited by a method such as, for example: a method which includesadding, e.g., a water-soluble organic solvent such as acetone or C1-C4alcohol to a reaction liquid after completing the reaction in the finalstep of the synthesis reaction of the compound represented by the aboveformula (1), or to an aqueous solution containing the compoundrepresented by the formula (1); a method which includes permittingsalting-out by adding sodium chloride; or the like. Also, after thusobtained wet cake of the sodium salt is dissolved in water, the pH ofthe solution is adjusted appropriately by adding an acid such ashydrochloric acid, and the deposited solid is isolated by filtration.Accordingly, a free acid of the compound represented by the aboveformula (1), or a mixture containing a sodium salt and a free acid ofthe compound represented by the formula (1), i.e., the compoundconverted into a sodium salt in part, can be also obtained.

Alternatively, after thus obtained wet cake of the sodium salt or a drysolid thereof is dissolved in water, thereto is added an ammonium saltsuch as ammonium chloride, and the pH of the solution is adjustedappropriately, for example, to a pH of 1 to 3, by adding an acid such ashydrochloric acid. An ammonium salt of the compound represented by theabove formula (1) can be obtained by isolating thus deposited solid byfiltration. By appropriately adjusting the amount of ammonium chlorideadded and/or the pH, a mixture containing an ammonium salt of thecompound of the formula (1) with a sodium salt of the compound of theformula (1); a mixture containing a free acid and an ammonium salt ofthe compound of the formula (1); and the like can be also obtained.

Alternatively, as described later, a free acid solid can be directlyobtained by adding a mineral acid (for example, hydrochloric acid,sulfuric acid or the like) to the reaction liquid after completing thereaction. In this regard, the wet cake of the free acid of the compoundof the formula (1) is added to water followed by stirring, and thenthereto may be added, for example, potassium hydroxide; lithiumhydroxide; aqueous ammonia; hydroxide of an organic quaternary ammoniumrepresented by the formula (6); or the like to permit production of asalt. Accordingly, a potassium salt; a lithium salt; an ammonium salt; aquaternary ammonium salt; or the like, that corresponds to each addedcompound can be obtained. By regulating the number of moles of theaforementioned salt added with respect to the number of moles of thefree acid, preparation of, for example: mixed salts of a lithium saltand a sodium salt, etc.; alternatively, mixed salts of a lithium salt, asodium salt, and an ammonium salt, etc. is also enabled. The salt of thecompound represented by the above formula (1) may have varying physicalproperties such as solubility, or performances of the inks when used asan ink, depending on the type of the salt thereof. Therefore, it is alsopreferred to select the type of the salt to meet intended performancesof the ink, and the like.

The compound of the present invention represented by the above formula(1) can be isolated in the form of a solid free acid by adding a mineralacid such as hydrochloric acid following completing the reaction, andinorganic salts such as e.g., sodium chloride and sodium sulfatecontained as impurities (i.e., inorganic impurities) can be removed bywashing the obtained solid free acid with water or acidic water such asaqueous hydrochloric acid, or the like. The free acid of the compound ofthe present invention obtained as described above in the form of a wetcake or a dry solid provided as mentioned in the foregoing, may besubjected to a treatment with a desired inorganic or organic base inwater, whereby a solution of the corresponding salt of the compound canbe obtained. The inorganic base includes, for example, hydroxides of analkali metal such as lithium hydroxide, sodium hydroxide and potassiumhydroxide; carbonates of an alkali metal such as lithium carbonate,sodium carbonate and potassium carbonate; or ammonium hydroxide (aqueousammonia), and the like. Examples of the organic base include organicamine corresponding to the quaternary ammonium represented by the aboveformula (6), for example, alkanolamines such as diethanolamine andtriethanolamine, and the like, but not limited thereto.

The compound of the present invention is suited for staining of naturaland synthetic fiber materials or blended fabric products, as well as forproduction of compositions of inks for ink jet recording, and writinginks. For example, a reaction liquid after completing the reaction inthe final step in the synthesis reaction of the compound of the presentinvention represented by the above formula (1) may be also used directlyfor producing an ink composition of the present invention. However,after isolating the compound by, for example, the aforementioned method,or drying the reaction liquid by spray drying or the like, the resultingcompound can be used to prepare an ink composition.

The ink composition of the present invention contains the compound ofthe above formula (1) in an amount of usually 0.1 to 20% by mass,preferably 1 to 10% by mass, and more preferably 2 to 8% by mass in thetotal mass of the ink composition.

The ink composition of the present invention is prepared by dissolvingthe compound represented by the above formula (1) in water or a mixedsolution (may be also referred to as “aqueous medium”) of water and awater-soluble organic solvent (organic solvent that is miscible withwater), and adding thereto an ink preparation agent as needed. When theink composition is used as an ink for ink jet printer, the content ofinorganic matter such as metal cation chlorides, for example, sodiumchloride etc., and sulfuric acid salts, for example, sodium sulfateetc., contained as impurities is preferably as low as possible. In thisregard, the total content of, for example, sodium chloride and sodiumsulfate accounts for about no greater than 1% by mass in total mass ofthe compound of the formula (1), and the lower limit may be 0% by mass,i.e., no greater than the detection limit of the analytical instrument.

A method for the production of the compound including less inorganicimpurities includes, for example: a method with a reverse osmoticmembrane well-known per se; a method which includes adding a driedmatter or wet cake of the compound of the present invention to, forexample, a water-soluble organic solvent such as acetone or a C1-C4alcohol (e.g., methanol, ethanol, isopropanol, etc.), or a water-solubleorganic solvent containing water, and subjecting the mixture topurification in suspension or crystallization; and the like. Adesalination treatment or the like may be carried out with any of thesemethods.

The ink composition of the present invention is prepared with water as amedium, and may appropriately contain a water-soluble organic solventand an ink preparation agent as needed in the range not to deterioratethe effects of the present invention.

The water-soluble organic solvent is used for the purpose of achievingfunctions such as dissolution of the dye; prevention of the compositionfrom drying (maintaining the wet state); adjustment of the viscosity ofthe composition; promotion of permeation of the coloring matter into therecord-receiving material; adjustment of the surface tension of thecomposition; defoaming of the composition; and the like, and thus and itis preferred that the water-soluble organic solvent is contained in theink composition of the present invention.

The ink preparation agent includes well-known additives such as, forexample, a preservative and fungicide, a pH adjusting agent, a chelatingreagent, a rust-preventive agent, an ultraviolet ray absorbing agent, aviscosity adjusting agent, a dye solubilizer, a discoloration-preventiveagent, an emulsification stabilizer, a surface tension adjusting agent,and a defoaming agent.

The content of the water-soluble organic solvent is 0 to 60% by mass,and preferably 10 to 50% by mass relative to the total mass of the inkcomposition of the present invention, whereas the ink preparation agentmay be used in an amount of 0 to 20% by mass, and preferably 0 to 15% bymass relative to the total mass of the ink composition of the presentinvention. In the ink composition of the present invention, theremaining component other than the compound of the above formula (1),the water-soluble organic solvent, and the ink preparation agent iswater.

The water-soluble organic solvent may be, for example: a C1-C4 alcoholsuch as methanol, ethanol, n-propanol, isopropanol, n-butanol,isobutanol, secondary butanol and tertiary butanol; an amide such asN,N-dimethylformamide and N,N-dimethylacetamide; heterocyclic ketonesuch as 2-pyrrolidone, N-methyl-2-pyrrolidone,hydroxyethyl-2-pyrrolidone, 1,3-dimethyl imidazolidin-2-one and1,3-dimethylhexahydropyrimid-2-one; ketone or a keto alcohol such asacetone, methylethylketone and 2-methyl-2-hydroxypentan-4-one; a cyclicether such as tetrahydrofuran and dioxane; a mono-, oligo-, orpoly-alkylene glycol or thioglycol having a (C2-C6)alkylene unit such asethylene glycol, 1,2- or 1,3-propylene glycol, 1,2- or 1,4-butyleneglycol, 1,6-hexylene glycol, diethylene glycol, triethylene glycol,tetraethylene glycol, dipropylene glycol, polyethylene glycol,polypropylene glycol and thiodiglycol; polyol (preferably triol) such astrimethylolpropane, glycerin and hexane-1,2,6-triol; (C1-C4)monoalkylether of a polyhydric alcohol such as ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether, diethylene glycol monobutyl ether(butylcarbitol), triethylene glycol monomethyl ether and triethyleneglycol monoethyl ether; γ-butyrolactone, dimethyl sulfoxide, and thelike.

It is to be noted that the water-soluble organic solvent described abovealso includes a substance that is solid at ambient temperatures such as,for example, trimethylolpropane, etc. However, the substance, etc.,exhibits solubility in water even if it is solid, and an aqueoussolution containing the substance, etc., has properties similar to thoseof water-soluble organic solvents and can be used for the same purposeas the water-soluble organic solvents. Therefore, also such solidsubstances are expediently included in the category of “water-solubleorganic solvent” herein, as long as they can be used for the purpose asdescribed above.

As the water-soluble organic solvent, preferable examples includeisopropanol, glycerin, mono-, di-, or tri-ethylene glycol, dipropyleneglycol, 2-pyrrolidone, hydroxyethyl-2-pyrrolidone,N-methyl-2-pyrrolidone, trimethylolpropane, and butylcarbitol, whereasmore preferable examples include isopropanol, glycerin, diethyleneglycol, 2-pyrrolidone, N-methyl-2-pyrrolidone, trimethylolpropane, andbutylcarbitol. These water-soluble organic solvents are used eitheralone or as a mixture.

The aforementioned preservative and fungicide may include, for example,a compound of organic sulfur based, organic nitrogen sulfur based,organic halogen based, haloallyl sulfone based, iodopropargyl based,N-haloalkylthio based, benzothiazole based, nitrile based, pyridinebased, 8-oxyquinoline based, isothiazoline based, dithiol based,pyridineoxide based, nitropropane based, organic tin based, phenolbased, quaternary ammonium salt based, triazine based, thiadiazinebased, anilide based, adamantane based, dithiocarbamate based,brominated indanone based, benzylbromoacetate based, inorganic saltbased or the like.

The organic halogen based compound may include, for example, sodiumpentachlorophenol.

The pyridineoxide based compound may include, for example, sodium2-pyridinethiol-1-oxide.

The isothiazoline based compound may include, for example,1,2-benzisothiazolin-3-one, 2-n-octyl-4-isothiazolin-3-one,5-chloro-2-methyl-4-isothiazolin-3-one,5-chloro-2-methyl-4-isothiazolin-3-one magnesiumchloride,5-chloro-2-methyl-4-isothiazolin-3-one calciumchloride,2-methyl-4-isothiazolin-3-one calciumchloride, and the like.

The other preservative and fungicide may be sodium acetate, sodiumsorbate, sodium benzoate, and the like, as well as trade names Proxel®GXL (S) and Proxel® XL-2 (S) manufactured by Arch Chemical, Inc., andthe like. As used herein, the superscript notation of “RTM” means aregistered trademark.

The pH adjusting agent may be used for the purpose of improving storagestability of the ink, and an arbitrary substance can be used as long asthe pH of the ink can be controlled to fall within the range of 6.0 to11.0. Examples of the pH adjusting agent include: alkanolamines such asdiethanolamine and triethanolamine; hydroxides of an alkali metal suchas lithium hydroxide, sodium hydroxide and potassium hydroxide; ammoniumhydroxide; carbonates of an alkali metal such as lithium carbonate,sodium carbonate and potassium carbonate; aminosulfonic acids such astaurine; and the like.

The chelating agent may include, for example, disodium ethylenediaminetetraacetate, sodium nitrilo triacetate, sodiumhydroxyethylethylenediamine triacetate, sodium diethylenetriaminepentaacetate, sodium uracil diacetate, and the like.

The rust-preventive agent may include, for example, acidic sulfite,sodium thiosulfate, ammonium thioglycolate, diisopropylammonium nitrite,pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and thelike.

Examples of the ultraviolet ray absorbing agent include benzophenonebased compounds, benzotriazole based compounds, cinnamic acid basedcompounds, triazine based compounds, stilbene based compounds, and thelike. Alternatively, a fluorescent whitening agent generally referredto, which is a compound that absorbs an ultraviolet ray to emitfluorescence, and which is typified by a benzoxazole based compound orthe like may be also used.

The viscosity adjusting agent may include in addition to thewater-soluble organic solvent, a water-soluble polymer compound, andspecific examples include polyvinyl alcohols, cellulose derivatives,polyamine, polyimine, and the like.

The dye solubilizer may include, for example, urea, ε-caprolactam,ethylene carbonate, and the like. Of these, it is preferred to use urea.

The discoloration-preventive agent is used for the purpose of improvingstorability of the image. As the discoloration-preventive agent, avariety of organic and metal complex based discoloration-preventiveagents may be used. Examples of the organic discoloration-preventiveagent include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols,anilines, amines, indanes, chromanes, alkoxyanilines, heterocycles andthe like, whereas examples of the metal complex include nickelcomplexes, zinc complexes and the like.

As the surface tension adjusting agent, surfactants may be exemplified,and examples include anionic surfactants, amphoteric surfactants,cationic surfactants, nonionic surfactants, and the like.

Examples of the anionic surfactant include alkylsulfocarboxylic acidsalts, α-olefinsulfonic acid salts, polyoxyethylenealkyl ether aceticacid salts, N-acylamino acid and salts thereof, N-acylmethyltaurinesalts, alkylsulfate polyoxyalkyl ether sulfuric acid salts, alkylsulfatepolyoxyethylenealkyl ether phosphoric acid salts, rosin acid soap,castor oil sulfate ester salts, lauryl alcohol sulfate ester salts,alkylphenolic phosphate esters, alkylated phosphate esters,alkylarylsulfonic acid salts, diethyl sulfosuccinic acid salts,diethylhexyl sulfosuccinic acid salts, dioctyl sulfosuccinic acid salts,and the like.

Examples of the cationic surfactant include 2-vinylpyridine derivatives,poly(4-vinylpyridine) derivatives, and the like.

Examples of the amphoteric surfactant include lauryldimethylaminoacetate betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazoliniumbetaine, coconut oil fatty acid amide propyldimethylamino acetatebetaine, polyoctylpolyaminoethylglycine, imidazoline derivatives, andthe like.

Examples of the nonionic surfactant include: ether based surfactantssuch as polyoxyethylene nonylphenyl ether, polyoxyethylene octylphenylether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene oleylether, polyoxyethylene lauryl ether and polyoxyethylene alkyl ether;ester based surfactants such as polyoxyethylene oleate esters,polyoxyethylene distearate esters, sorbitan laurate, sorbitanmonostearate, sorbitan monooleate, sorbitan sesquioleate,polyoxyethylene monooleate and polyoxyethylene stearate; acetyleneglycol (alcohol) based surfactants such as2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-dioland 3,5-dimethyl-1-hexyn-3-ol; trade names Surfynol® 104, 82 and 465,and Olfin® STG manufactured by Nissin Chemical Co., Ltd.; trade nameTergitol® 15-S-7 manufactured by Sigma-Aldrich Corporation; and thelike.

Examples of the defoaming agent include highly oxidized oil basedcompounds, glycerin fatty acid ester based compounds, fluorine basedcompounds, silicone based compounds, and the like.

These ink preparation agents may be used either alone or as a mixture.The surface tension of the ink composition of the present invention isusually 25 to 70 mN/m, and more preferably 25 to 60 mN/m, whereas theviscosity of the ink composition is adjusted to preferably no greaterthan 30 mPa·s, and more preferably no greater than 20 mPa·s.

In production of the ink composition of the present invention, the orderof dissolving each reagent such as additives is not particularlylimited. Water employed when the composition is prepared preferablyincludes impurities in an amount as low as possible, and thus water suchas ion exchanged water or distilled water is preferred. Furthermore,precision filtration may be carried out to remove contamination in theink composition, as needed after the ink composition is prepared, usinga membrane filter or the like. In particular, when the ink compositionof the present invention is used as an ink for ink jet recording,carrying out the precision filtration is preferred. The filter for usein precision filtration has a pore size of usually 1 μm to 0.1 μm, andpreferably 0.8 μm to 0.1 μm.

The ink composition containing the compound of the present invention issuited for use in printing, copying, marking, writing, drawing,stamping, or recording (printing), and particularly in ink jetrecording. In addition, the ink composition of the present invention isless likely to be deposited as solids even though dried in the vicinityof the nozzle of recording heads of an ink jet printer, and therefore,clogging of the recording head is also less likely to occur based on thesame reason.

A process for recording on a record-receiving material with the ink jetrecording method of the present invention may be as in the following.More specifically, in the process, a vessel filled with the inkcomposition is attached at a specified position of an ink jet printer,and the recording is executed by discharging ink droplets in response torecording signals using the ink composition of the present invention asan ink to allow the droplets to adhere onto a record-receiving material.There are ink jet printers in which, for example, a piezo systemutilizing mechanical vibration; a bubble jet (registered trademark)system utilizing bubbles generated by heating; or the like is adopted.The ink jet recording method of the present invention can be employedaccording to any system.

In some cases, two kinds of inks containing the same coloring matter areloaded in one ink jet printer for the purpose of obtaining a higherdefinition image. The difference between these two kinds of inks is thecontent of the coloring matter, and one ink having a higher content andanother ink having a lower content are used as an ink set. The inkcomposition of the present invention may be used as such an ink set.Also, one of the ink set may contain the ink composition of the presentinvention, whereas another may contain a well-known ink (composition).

The ink composition of the present invention may be provided as a yellowink composition containing the compound of the present invention and awell-known yellow coloring matter in the range not to inhibit theeffects achieved by the present invention, for the purpose of fineadjustment of the hue and the like. In addition, the compound of thepresent invention may be also used for applications in colorconditioning of other colors, for example, of a black ink, or for thepurpose of preparing a red ink or a green ink by using in combinationwith a magenta coloring matter or a cyan coloring matter. Furthermore,each ink of magenta and cyan, as well as if necessary, green, blue (orviolet), red, black and the like may be used in combination with the inkcomposition of the present invention for the purpose of obtaining a fullcolor recorded image. In this case, the ink of each color may be filledin each vessel, and the vessels may be attached at a specified positionof the ink jet printer and then used.

The record-receiving material for use in the ink jet recording method ofthe present invention may include, for example, a communication sheetsuch as a paper or film, a fiber or cloth (cellulose, nylon, wool,etc.), a leather, a substrate for color filters and the like, and acommunication sheet is preferred. The communication sheet is notparticularly limited, and not only plain paper, but also a sheetsubjected to a surface treatment, specifically, a sheet having an inkreceiving layer provided on a base material such as paper, syntheticpaper, films and the like may be used.

The ink receiving layer has a function of absorbing the ink andaccelerating the drying thereof. The ink receiving layer is provided by,for example: a method in which a cation based polymer is impregnated inor coated on the aforementioned base material; a method in whichinorganic fine particles that can absorb a coloring matter in an ink arecoated on the surface of the aforementioned base material together witha hydrophilic polymer such as polyvinyl alcohol or polyvinylpyrrolidone.The material entity of the inorganic fine particles that can absorb acoloring matter in an ink may include porous silica, alumina sol,special ceramics, and the like. Such communication sheets having an inkreceiving layer are generally referred to as exclusive ink jet paper,exclusive ink jet film, glossy paper, gloss film, and the like. Examplesof typical commercially available products of the communication sheethaving an ink receiving layer include trade names: Professional PhotoPaper, and Glossy Gold manufactured by Canon, Inc.; trade names: PhotoPaper CRISPIA (Super Glossy), and Photo Paper (Glossy) manufactured bySeiko Epson Corporation; trade name: Advanced Photo Paper (Glossy)manufactured by Hewlett-Packard Japan, Ltd.; trade name: KASSAISHASHIN-SHIAGE Pro manufactured by FUJIFILM Corporation; and the like.

Further, the plain paper means a paper which is not provided with an inkreceiving layer in particular, and a variety of plain paper has beenavailable in the market depending on their intended use. Of commerciallyavailable plain paper, examples for ink jet printing include: Plainpaper with high quality on both faces (manufactured by Seiko EpsonCorporation); PB PAPER GF-500 (manufactured by Canon, Inc.);Multipurpose Paper, All-in-one Printing Paper (manufactured by HewlettPackard Co.); and the like. Additionally, plane paper copy (PPC) paperand the like for which the intended use is not particularly limited toink jet recording is also included in the plain paper.

The colored article of the present invention means a substance which wascolored with any one of: (a) the water-soluble azo compound of thepresent invention; (b) the ink composition of the present inventioncontaining the compound; or (c) the ink composition of the presentinvention containing the compound and a water-soluble organic solvent.The substance colored is not particularly limited, and may include forexample, the aforementioned record-receiving materials, and the like,but not limited thereto. Preferably the aforementioned record-receivingmaterials colored may be exemplified. Although not particularly limited,the coloring method of the substance may include, for example, printingmethods such as a dip dyeing method, a textile printing method and ascreen printing, as well as the ink jet recording method of the presentinvention, and the like, but the ink jet recording method of the presentinvention is preferred. Among the aforementioned colored articles, acolored article which was colored by the ink jet recording method of thepresent invention is preferred.

The water-soluble azo compound of the present invention represented bythe above formula (1) is extremely superior in solubility in water andwater-soluble organic solvents. Additionally, the water-soluble azocompound is characterized by having favorable filterability on, forexample, membrane filters, in the step of producing an ink compositionof the present invention.

The ink composition of the present invention provides yellow recordedimages that are very brilliant, and having a high chroma saturation andprint density, and ideal hue on record-receiving materials such as plainpaper and communication sheets having an ink receiving layer. Thus,strict reproduction of photographic color images on paper is enabled.Moreover, the ink composition of the present invention exhibitsextremely favorable storage stability, without solid deposition,physical property alteration, change in the hue and the like afterstorage for a long period of time. Even if the ink composition of thepresent invention is used as an ink jet ink, deposition of solids due todrying of the ink composition in the vicinity of the nozzle hardlyoccurs, and clogging of the injector (recording head) can be alsoavoided.

Also, the ink composition of the present invention does not causealteration of physical properties even when the ink is used by recyclingwith a comparatively long time interval using a continuous ink jetprinter, or even when intermittently used with an on-demand ink jetprinter. Still further, images recorded on a communication sheet havingan ink receiving layer with the ink composition of the present inventionhas favorable various types of fastness properties such as waterresistance, moisture resistance, ozone gas resistance, frictionresistance and light resistance, particularly superior light resistanceand ozone gas resistance. For this reason, superior long-term storagestability of photographic image is also achieved. Also, superiorcoloring properties such as chroma saturation, brightness, and printdensity on plain paper are attained as compared with conventional inks.

Accordingly, a water-soluble azo compound of the present inventionrepresented by the formula (1), and the ink composition of the presentinvention containing the same are extremely useful for applications asvarious types of recording inks, particularly applications as inks forink jet recording.

EXAMPLES

Hereinafter, the present invention is more specifically described belowby way of Examples, but it is not to be construed as being limitedthereto. In the specification, unless otherwise stated particularly, theexpressions “part” and “%” are on the basis of the mass, and thereaction temperature means an interior temperature.

With respect to some of the compounds synthesized, λmax (wavelength ofmaximum absorption) shows the value of measurement in an aqueoussolution of pH 7 to 8.

Also, in each structural formula of the compounds obtained in Examples,the acidic functional group such as a carboxy group or a sulfo group isrepresented in the form of its free acid.

In Examples, the target substance crystallized using acetone could besimilarly crystallized also when isopropanol was used in place ofacetone.

It should be noted that, solubility in water at room temperature of anyof the compounds of the present invention obtained in Examples was noless than 100 g/L.

Example 1 Step 1

5-Aminoisophthalic acid in an amount of 18.1 parts was dissolved in 200parts of water while adjusting the pH to 6 with sodium hydroxide, andthen 7.2 parts of sodium nitrite were added thereto. After this solutionwas added dropwise to 200 parts of 5% hydrochloric acid at 0 to 10° C.over 30 min, the mixture was stirred at no higher than 10° C. for 1 hourto carry out a diazotization reaction, whereby a diazo reaction liquidwas prepared. On the other hand, 26.6 parts of2-(sulfopropoxy)-5-chloroaniline were dissolved in 130 parts of waterwhile adjusting the pH to 7 with sodium hydroxide and converted into amethyl-ω-sulfonate derivative using 10.4 parts of sodium bisulfite and8.6 parts of 35% formalin by a routine method. Thus obtainedmethyl-ω-sulfonate derivative was added to the diazo reaction liquidprepared beforehand, and the mixture was stirred at 0 to 15° C. and a pHof 2 to 4 for 24 hrs. After the pH of the reaction liquid was adjustedto 11 with sodium hydroxide, the liquid was stirred while maintainingthe same pH at 80 to 95° C. for 5 hrs. Thus resulting reaction liquidwas added dropwise to 200 parts of 5% hydrochloric acid, and thedeposited solid was isolated by filtration to obtain 100 parts of an azocompound represented by the following formula (7) as wet cake.

Step 2

Into 250 parts of ice water were added 0.10 parts of Leocol® TD90 (tradename, surfactant) manufactured by Lion Corporation, and the mixture wasvigorously stirred, to which 3.6 parts of cyanuric chloride were added,followed by stirring at 0 to 5° C. for 30 min to obtain a suspension.Subsequently, the wet cake of the compound represented by the aboveformula (7) in an amount of 100 parts was dissolved in 200 parts ofwater, and the aforementioned suspension was added dropwise to thissolution over 30 min. After completing the dropwise addition, themixture was stirred at a pH of 6 to 8 and at 25 to 45° C. for 6 hrs.Subsequently, 6.0 parts of glycine were added thereto followed bystirring at a pH of 7 to 9 and at 75 to 90° C. for 4 hrs. After coolingthe obtained reaction liquid to 20 to 25° C., 800 parts of acetone wereadded to this reaction liquid, followed by stirring at 20 to 25° C. for1 hour. The deposited solid was isolated by filtration to obtain 50.0parts of wet cake. This wet cake was dried with a hot-air dryer at 80°C. to obtain 13.0 parts of a sodium salt of the water-soluble azocompound (λmax: 401.5 nm) of the present invention represented by thefollowing formula (8).

Example 2

In a similar manner to Example 1 except that 8.0 parts of β-alanine wereused in place of 6.0 parts of glycine in the Step 2 of Example 1, 13.5parts of a sodium salt of the water-soluble azo compound (λmax: 403 nm)of the present invention represented by the following formula (9) wereobtained.

Example 3

In a similar manner to Example 1 except that 12.0 parts of6-aminohexanoic acid were used in place of 6.0 parts of glycine in theStep 2 of Example 1, 14.5 parts of a sodium salt of the water-solubleazo compound (λmax: 404 nm) of the present invention represented by thefollowing formula (10) were obtained.

Examples 4 to 6 (A) Preparation of Ink

Using each of the azo compounds (sodium salts represented by theformulae (8) to (10)) of the present invention obtained in theaforementioned Examples 1 to 3 as a coloring matter, the ink compositionof the present invention was obtained by mixing the blend shown in thefollowing Table 3 to prepare a solution. Thus obtained ink compositionwas each filtered through a 0.45 μm membrane filter to removecontaminants, whereby an ink for test was prepared. The pH of this inkfor test was in the range of 8.0 to 9.5. In the following Table 3,“Surfactant” employed was trade name Surfynol® 104PG50 manufactured byNissin Chemical Co., Ltd. Preparations of the inks using the compoundsobtained in Examples 1, 2, and 3 are designated as Examples 4, 5, and 6,respectively.

TABLE 3 Blend of ink composition Compound obtained in 3.5 parts eachExample Glycerin 5.0 parts Urea 5.0 parts N-methyl-2-pyrrolidone 4.0parts Isopropyl alcohol 3.0 parts Butylcarbitol 2.0 parts Surfactant 0.1parts Ion exchanged water 77.4 parts Total 100.0 parts

Comparative Example 1

Comparative ink was prepared in a similar manner to Examples 4 to 6except that a coloring matter disclosed in Example 10 of Patent Document1 was used in place of the azo compound obtained in Examples 1 to 3. Thepreparation of this ink is designated as Comparative Example 1. Thestructural formula of the compound used in Comparative Example 1 isshown in the following formula (11).

Comparative Example 2

Comparative ink was prepared in a similar manner to Examples 4 to 6except that a coloring matter disclosed in Example 2 of Patent Document2 was used in place of the azo compound obtained in Examples 1 to 3. Thepreparation of this ink is designated as Comparative Example 2. Thestructural formula of the compound used in Comparative Example 2 isshown in the following formula (12).

(B) Ink Jet Recording

Using an ink jet printer (manufactured by Canon, Inc., trade name:PIXUS® ip4100), ink jet recording was carried out on three kinds of theglossy paper described below (exclusive ink jet paper) with each inkprepared in the aforementioned Examples 4 to 6, and Comparative Examples1 to 2. Upon ink jet recording, an image pattern recorded at eachdensity of 100%, 85%, 70%, 55%, 40% and 25% was produced such thatseveral-step gradation of the reflected density was obtained, whereby ayellow recorded article was produced. Using thus obtained recordedarticle as a test piece, various types of tests were performed.

Glossy paper 1: manufactured by Canon, Inc., trade name: Canon PhotoPaper Glossy Pro (Platinum Grade)

Glossy paper 2: manufactured by Seiko Epson Corporation, trade name:Photo Paper CRISPIA (Super Glossy)

Glossy paper 3: manufactured by Brother Industries, Ltd., trade name:Photo Glossy Paper BP71G

For the light resistance test and the ozone gas resistance test,reflected density was determined on a part where the reflected density,i.e., D value, of the recorded article before the test was mostapproximate to 1.0. For measurement of the reflected density, acolorimetric system (trade name SpectroEye®, manufactured by X-Rite Co.,Ltd.) was used. The colorimetric determination was carried out under acondition of a viewing angle of 2°, and a light source of D65, with adensity standard of DIN. Various test methods, and evaluation methods ofthe test results of the recorded image are described below.

(C) Print Density of Recorded Matter

With respect to a part having a reflected density of 70% described aboveon each test piece, the value of yellow density Dy was measured with theaforementioned colorimetric system. Evaluation criteria are as in thefollowing. Dy value and results of evaluation are shown in Table 4below.

Dy value being no less than 1.85: A

Dy value being less than 1.85 and no less than 1.75: B

Dy value being less than 1.75: C

(D) Xenon Light Resistance Test

Each test piece was put into a holder, and irradiated at an illuminanceof 0.36 W/m², at a temperature of 24° C., and a humidity of 60% RH usinga Xenon Weather Meter XL75 (manufactured by Suga Test Instruments Co.,Ltd.) for 168 hrs. The colorimetric determination was carried on a parthaving a reflected density of 70% described above on each test pieceafter the testing using the aforementioned colorimetric system. Theresidual ratio of the coloring matter was determined by calculationaccording to the formula of: (reflected density after test/reflecteddensity before test)×100(%), and evaluation was made by rating on athree point scale. The residual ratio of the coloring matter and resultsof evaluation are shown in Table 5 below.

Residual ratio of the coloring matter being no less than 70%: A

Residual ratio of the coloring matter being less than 70% and no lessthan 60%: B

Residual ratio of the coloring matter being less than 600: C

(E) Ozone Gas Resistance Test

After each test piece was left to stand under a condition of: an ozoneconcentration of 10 ppm; a humidity of 60% RH; and a temperature of 24°C., using an Ozone Weather Meter (manufactured by Suga Test InstrumentsCo., Ltd.) for 16 hrs, the colorimetric determination was carried on apart having a reflected density of 70% described above on each testpiece after the testing using the aforementioned colorimetric system.The residual ratio of the coloring matter was determined by calculationaccording to the formula of: (reflected density after test/reflecteddensity before test)×100(%), and evaluation was made by rating on athree point scale. The residual ratio of the coloring matter and resultsof evaluation are shown in Table 6 below.

Residual ratio of the coloring matter being no less than 85%: A

Residual ratio of the coloring matter being less than 85% and no lessthan 80%: B

Residual ratio of the coloring matter being less than 80%: C

TABLE 4 Results of print density test (part having a Glossy GlossyGlossy density of 70%) paper 1 paper 2 paper 3 Example 4 A (1.94) A(2.04) A (2.13) Example 5 A (1.88) A (1.88) A (1.95) Example 6 A (1.95)A (2.01) A (2.05) Comparative Example 1 C (1.66) C (1.69) B (1.84)Comparative Example 2 B (1.81) A (1.88) A (2.01)

TABLE 5 Results of xenon light resistance test (part having GlossyGlossy Glossy a density of 70%) paper 1 paper 2 paper 3 Example 4 A(78.7) A (77.7) A (78.5) Example 5 A (78.1) A (83.3) A (81.7) Example 6A (75.0) A (73.7) A (76.3) Comparative Example 1 C (47.4) C (56.2) C(59.5) Comparative Example 2 C (54.3) C (59.0) B (61.1)

TABLE 6 Results of ozone gas resistance test (part having Glossy GlossyGlossy a density of 70%) paper 1 paper 2 paper 3 Example 4 A (90.2) A(90.6) A (85.9) Example 5 A (90.4) A (92.5) A (88.9) Example 6 A (90.8)A (92.5) A (89.9) Comparative Example 1 A (91.8) A (96.2) A (95.7)Comparative Example 2 B (80.0) C (77.8) C (75.4)

From the results shown in Table 4 and Table 5, Comparative Example 1exhibited extremely inferior results in both tests of the print densityand xenon light resistance, as compared with each Example. In addition,Comparative Example 2 exhibited extremely inferior results in both testsof the xenon light resistance and ozone gas resistance, as compared witheach Example. In contrast, each Example exhibited superior results inall tests of the print density, xenon light resistance and ozone gasresistance.

From the foregoing test results, the inks of Examples 4 to 6 containingthe azo compound the present invention indicated a high print density,and were also revealed to be superior in fastness properties such aslight resistance and ozone gas resistance.

Example 7

In a similar manner to Example 1 except that 21.0 parts of aspartic acidwere used in place of 6.0 parts of glycine in the Step 2 of Example 1,13.0 parts of a sodium salt of the water-soluble azo compound (λmax:405.0 nm) of the present invention represented by the following formula(13) were obtained.

Example 8

In a similar manner to Example 1 except that 23.0 parts of glutamic acidwere used in place of 6.0 parts of glycine in the Step 2 of Example 1,13.5 parts of a sodium salt of the water-soluble azo compound (λmax:406.5 nm) of the present invention represented by the following formula(14) were obtained.

Examples 9 and 10 (F) Preparation of Ink

Using each of the azo compounds (sodium salts represented by the formula(13) and the formula (14)) of the present invention obtained in theaforementioned Examples 7 and 8 as a coloring matter, the inkcomposition of the present invention was obtained by mixing the blendshown in the above Table 3 to prepare a solution. Thus obtained inkcomposition was each filtered through a 0.45 μm membrane filter toremove contaminants, whereby an ink for test was prepared. The pH ofthis ink for test was in the range of 8.0 to 9.5. Preparations of theinks using the compounds obtained in Examples 7 and 8 are designated asExamples 9 and 10, respectively.

(G) Ink Jet Recording

Using an ink jet printer (manufactured by Canon, Inc., trade name:PIXUS® ip4500), ink jet recording was carried out on three kinds of theglossy paper described below (exclusive ink jet paper) with each inkprepared in the aforementioned Examples 9 and 10, and ComparativeExamples 1 to 2. Upon ink jet recording, an image pattern recorded ateach density of 100%, 85%, 70%, 55%, 40% and 25% was produced such thatseveral-step gradation of the reflected density was obtained, whereby arecorded article having yellow gradation was produced. Using thusobtained recorded article as a test piece, various types of tests wereperformed.

Glossy paper 1: manufactured by Canon, Inc., trade name: Canon PhotoPaper Glossy Pro (Platinum Grade)

Glossy paper 2: manufactured by Seiko Epson Corporation, trade name:Photo Paper CRISPIA (Super Glossy)

Glossy paper 3: manufactured by Brother Industries, Ltd., trade name:Photo Glossy Paper BP71G

For the light resistance test and the ozone gas resistance test,reflected density was determined on a part where the reflected density,i.e., D value, of the recorded matter before the test was mostapproximate to 1.0. For measurement of the reflected density, acolorimetric system (trade name SpectroEye®, manufactured by X-Rite Co.,Ltd.) was used. The colorimetric determination was carried out under acondition of a viewing angle of 2°, and a light source of D65, with adensity standard of DIN. Various test methods, and evaluation methods ofthe test results of the recorded image are described below.

(H) Chroma Saturation Test

With respect to a part having a reflected density of 70% described aboveon each test piece, the value of yellow chroma saturation C⁺ wasmeasured with the aforementioned colorimetric system. Evaluationcriteria are as in the following. C⁺ value and results of evaluation areshown in Table 7 below.

C⁺ value being no less than 100: A

C⁺ value being less than 100 and no less than 95: B

C⁺ value being less than 95: C

(I) Xenon Light Resistance Test

Each test piece was put into a holder, and irradiated at an illuminanceof 0.36 W/m², at a temperature of 24° C., and a humidity of 60% RH,using a Xenon Weather Meter XL75 (manufactured by Suga Test InstrumentsCo., Ltd.) for 168 hrs. The colorimetric determination was carried on apart having a reflected density of 70% described above on each testpiece after the testing using the aforementioned colorimetric system.The residual ratio of the coloring matter was determined by calculationaccording to the formula of: (reflected density after test/reflecteddensity before test)×100(%), and evaluation was made by rating on athree point scale. The residual ratio of the coloring matter and resultsof evaluation are shown in Table 8 below.

Residual ratio of the coloring matter being no less than 80%: A

Residual ratio of the coloring matter being less than 80% and no lessthan 75%: B

Residual ratio of the coloring matter being less than 750: C

(J) Ozone Gas Resistance Test

After each test piece was left to stand under a condition of: an ozoneconcentration of 10 ppm; a humidity of 60% RH; and a temperature of 24°C., using an Ozone Weather Meter (manufactured by Suga Test InstrumentsCo., Ltd.) for 16 hrs, the colorimetric determination was carried on apart having a reflected density of 70% described above on each testpiece after the testing using the aforementioned colorimetric system.The residual ratio of the coloring matter was determined by calculationaccording to the formula of: (reflected density after test/reflecteddensity before test)×100(%), and evaluation was made by rating on athree point scale. The residual ratio of the coloring matter and resultsof evaluation are shown in Table 9 below.

Residual ratio of the coloring matter being no less than 90%: A

Residual ratio of the coloring matter being less than 90% and no lessthan 80%: B

Residual ratio of the coloring matter being less than 80%: C

TABLE 7 Results of chroma saturation test (part having Glossy GlossyGlossy a density of 70%) paper 1 paper 2 paper 3 Example 9 A (104) A(110) A (109) Example 10 A (103) A (113) A (110) Comparative Example 1 C(94) C (91) C (90) Comparative Example 2 A (103) A (103) A (101)

TABLE 8 Results of xenon light resistance test (part having GlossyGlossy Glossy a density of 70%) paper 1 paper 2 paper 3 Example 9 A(82.6) A (87.5) A (83.2) Example 10 A (81.7) A (83.3) A (83.4)Comparative Example 1 C (61.9) C (59.6) C (71.8) Comparative Example 2 C(71.1) B (76.0) B (78.4)

TABLE 9 Results of ozone gas resistance test (part having Glossy GlossyGlossy a density of 70%) paper 1 paper 2 paper 3 Example 9 A (93.0) A(96.2) A (96.3) Example 10 A (92.9) A (96.8) A (96.9) ComparativeExample 1 A (95.0) A (99.4) A (99.4) Comparative Example 2 B (89.8) A(93.4) A (94.2)

From the results shown in Table 7 to Table 9, Comparative Example 1exhibited extremely inferior results in both tests of the chromasaturation and xenon light resistance, as compared with each Example. Inaddition, Comparative Example 2 exhibited favorable results in thechroma saturation test, and the ozone gas resistance test conductedusing Glossy paper 2 and 3; however, in both the xenon light resistance,and the ozone gas resistance test conducted using Glossy paper 1,inferior results as compared with each Example were exhibited. Incontrast, each Example exhibited extremely superior results in all testsof the chroma saturation of the recorded matter, and the xenon lightresistance and ozone gas resistance.

(K) Xenon Light Resistance Test

Similarly to the aforementioned “(I) Xenon Light Resistance Test” exceptthat the colorimetric determination was carried on a part having areflected density of 55% on each test piece, the residual ratio of thecoloring matter was determined by calculation. The results are shown inTable 10 below.

(L) Ozone Gas Resistance Test

Similarly to the aforementioned “(J) Ozone Gas Resistance Test” exceptthat the colorimetric determination was carried on parts having areflected density of 70% and 55%, respectively, on each test piece, andthat the time period of leaving to stand was 40 hrs, the residual ratioof the coloring matter was determined by calculation. The results areshown in Table 11 and Table 12 below.

TABLE 10 Results of xenon light resistance test (part having GlossyGlossy Glossy a density of 55%) paper 1 paper 2 paper 3 Example 9 73.783.3 76.5 Example 10 72.7 73.3 76.7 Comparative Example 1 36.5 43.1 55.0Comparative Example 2 54.2 59.3 62.7

TABLE 11 Results of ozone gas resistance test (part having Glossy GlossyGlossy a density of 70%) paper 1 paper 2 paper 3 Example 9 90.1 88.088.0 Example 10 89.3 88.7 85.0 Comparative Example 1 89.4 87.6 83.3Comparative Example 2 77.1 65.7 59.5

TABLE 12 Results of ozone gas resistance test (part having Glossy GlossyGlossy a density of 55%) paper 1 paper 2 paper 3 Example 9 90.9 90.784.3 Example 10 88.9 85.3 82.8 Comparative Example 1 90.6 89.2 80.2Comparative Example 2 80.2 65.7 57.6

From the results shown in Table 10 to Table 12, the recorded imagesobtained with the inks of Comparative Example 1 and Comparative Example2 indicated a significantly reduced residual ratio of the coloringmatter particularly in the xenon light resistance test as the coloringmatter density is lower, all exhibiting inferior results as comparedwith each Example. In contrast, the recorded image obtained with the inkof each Example indicated a higher residual ratio of the coloring matterthan each Comparative Example even in a part having a low coloringmatter density, suggesting superior light resistance and ozone gasresistance.

INDUSTRIAL APPLICABILITY

The water-soluble azo compound of the present invention that is a yellowcoloring matter, and a yellow ink composition of the present inventioncontaining the same have a high print density, and provide recordedimages having a high chroma saturation. In addition thereto, they arealso superior in fastness properties such as light resistance and ozonegas resistance. Therefore, the compound, and an ink compositioncontaining the compound are very useful for various types ofapplications in recording, particularly applications in ink jetrecording.

The invention claimed is:
 1. A water-soluble azo compound represented bythe following formula (1) or a salt thereof:

wherein, Q represents a halogen atom; R represents a C1-C11 alkylenegroup; p represents an integer of 2 to 4; and n represents 1 or
 2. 2.The water-soluble azo compound or a salt thereof according to claim 1,wherein the water-soluble azo compound is represented by the followingformula (2):

wherein, q represents an integer of 1 to 11, and Q and p are as definedin the formula (1).
 3. The water-soluble azo compound or a salt thereofaccording to claim 2, wherein in the above formula (2), p is 3, and qrepresents an integer of 1 to
 5. 4. The water-soluble azo compound or asalt thereof according to claim 2, wherein the water-soluble azocompound is represented by the following formula (3):


5. The water-soluble azo compound or a salt thereof according to claim1, wherein the water-soluble azo compound is represented by thefollowing formula (4):

wherein, r represents an integer of 1 to 4, and Q and p are as definedin the formula (1).
 6. The water-soluble azo compound or a salt thereofaccording to claim 5, wherein in the above formula (4), Q is a chlorineatom; p is 3; and r is 1 or
 2. 7. The water-soluble azo compound or asalt thereof according to claim 5, wherein the water-soluble azocompound is represented by the following formula (5):


8. An ink composition comprising the water-soluble azo compound or asalt thereof according to claim
 1. 9. The ink composition according toclaim 8 further comprising a water-soluble organic solvent.
 10. The inkcomposition according to claim 8, wherein the ink composition isutilized in ink jet recording.
 11. An ink jet recording methodcomprising: discharging ink droplets in response to recording signalsutilizing the ink composition according to claim 8 as an ink to allowthe droplets to adhere onto a record-receiving material therebyexecuting recording.
 12. The ink jet recording method according to claim11, wherein the record-receiving material is a communication sheet. 13.The ink jet recording method according to claim 12, wherein thecommunication sheet is a plain paper or a sheet having an ink receivinglayer containing a porous white inorganic substance.
 14. A coloredarticle which is colored with any one of: (a) the water-soluble azocompound or a salt thereof according to claim 1; (b) an ink compositioncontaining the water-soluble azo compound or a salt thereof according toclaim 1; or (c) an ink composition containing the water-soluble azocompound or a salt thereof according to claim 1 and a water-solubleorganic solvent.
 15. A colored matter wherein the coloring is carriedout with the ink jet recording method according to claim
 11. 16. An inkjet printer equipped with a vessel containing the ink compositionaccording to claim 8.